Process of tanning hides, skins, or other animal tissues.



UNITED STATES PATENT OFFICE.

OTTO P. AMEND, OF NEW YORK, N. Y.

PROCESS OF TANNING HIDES, SKINS, OR OTHER ANIMAL TISSUES;

SPECIFICATION forming part of Letters Patent N 0. 72 5,648, dated April21, 1903.

Application filed March 27, 1901. Serial No. 53,135. (No specimens.)

To all whom it may concern.-

Be it known that I, Orro P. AMEND, a citizen of the United States,residing in the city, county, and State of New York, have invented acertain new and useful Process for the Tanning of Hides, Skins, or otherAnimal Tissues, of which the followingis a specification.

After many experiments I have found that the nitrites of theleather-forming metals are eminently suited to the tanning or tawing ofhides and skins. In a former application,filed January 28, 1901, SerialNo. 44,704, I have described and claimed the preparation and use of newtanning liquors containing a nitrite of a leather-forming metal in anaqueous solution. The present invention is based on the discovery thatsuch nitrites and salts of nitrousacid when introduced into or formed intanning liquors (such as organic tanning liquors made from sumac,hemlock, gambier, quebracho, oak, and other barks and materialscontaining tannin) and metallic tanning liquors containing theleather-forming metals greatly improve,expedite,and cheapen theoperation and that when used in aqueous solution upon the hide or skinwhich has'already been converted into leather such leather is therebygreatly improved. I have found, further, that by the use of atanning-bath containing a nitrite of a leather-forming metal theoperation of treating the hides or skins with dung or manure may beentirely dispensed with, as it is unnecessary, though of course it maybe used if desired. I have also discovered that the skin may be tannedby my process without removing the hair and that if dehairing is desiredthe liming, dehairing, and subsequent removal of the lime may beperformed either before or after the pelt or skin has been tanned in mysolutions. If liming and dehairing are practiced, I prefor to remove thelime chemically by washing in a weak solution of an acid, such asmuriatic or acetic acid. As nitrited tanning solutions readily penetratehides and skins in any condition and have an affinity therefor incontradistinctiou to other non-nitrited solutions which are repelled bythe skin or are repellent thereto, hides and skins intended for forpurposes may be thoroughly tanned by my solutions without suchpreliminary preparations of puring (or treatment with dung) anddegreasing, and the process results in a leather which is much strongerthan that produced by tawing liquors, which do not contain the nitritesof the leather-forming metals and are tawed without any appreciableshrinkage of the hide or skin, while in addition such skin will stand ahigher degree of heat in the dyeing of its hair or fur than leatherproduced by other processes, and, furthermore, there Will be noappreciable shrinkage in the dyeing operation.

In practicing my invention I first prepare an aqueous solutioncontaining a nitrite of one of the leather-forming metals-chromium,iron, and aluminium-and such solution may be formed in several ways.Thus, for instance, I dissolve a salt of one of such metals in water atordinary temperatures. I also dissolve a soluble nitrite of an alkalimetalsuch as nitrite of sodium, nitrite of potassium, &c.-,or of analkaline earth, such as nitrite of barium, in water at ordinarytemperatures and then mix the two solutions containing a nitrite of aleather-forming metal. In some cases there will be an insolubleprecipitate formed, together with a solution of a nitrite-of theleather-forming metal contained in the metallic salt, while in othercases no precipitate will be formed, but a partial decomposition takesplace witn the formation of a nitrite of the leather-forming metal inthe solution. In the former instance t-he precipitate may be removed byfiltration or decantation, as is well understood, while in both cases itis the solution containing the nitrite of the leather-forming metal thatfurnishes the tanning agent. As illustrations of the first class ofsolutions I dissolve seven hundred and seventeen (the molecular weight)grams of crystalline chromic sulfate, Or,(SO,) -|-l8(H O,) in aboutseven thousand grams of Water at ordinary temperatures. I also dissolvesix hundred and eighty-seven (three times the molecular weight) grams ofbarium nitrite, Ba(NO in about seven thousand grams of water at ordinarytemperatures. I then mix the two solutions and remove the insolubleprecipitate. The clear solution will contain nitrite of chromium and isthe tanning liquor to be used. Again, I dissolve three hundred of thelatter.

and sixty-nine (the molecular weight) grams of chromium oxalate, Cr (OO,) in about four thousand grams of water at ordinary temperatures. Ialso dissolve three hundred and ninety-six (three times the molecularweight) grams of calcium nitrite, Oa(NO in about four thousand grams ofwater. I then mix the.

two solutions and remove the precipitate. The clear solution willcontain nitrite of chromium and is the tanning liquor to be used. Ofcourse the salts may be mechanically mixed first and then dissolved inwater. As illustrations of the second class of solutions I have foundthat when I mix an aqueous so lution of a chlorid acetate, formate, ornitrate of one of the leather-forming metals with an aqueous solution ofa nitrite of an alkali metal or of an alkaline earth no precipitate maybe formed, but a reaction occurs, forming an aqueous solution containinga nitrite of a leather-forming metal, which is the tanning agent to beused. I have also found by experiment that I can form an efficient andcheap tanning solution of the second class by the use of chrome-alum, KOr (SO +24(H O,)as follows: Idissolve chromealum in, say, ten parts ofWater at ordinary temperatures and add to this solution a solution ofsodium nitrite in, say, ten parts of water at ordinary temperatures, theproportion of chrome-alum to sodium nitrate being one molecule of theformer to six molecules There will be no precipitate formed in thissolution, but there will be a reaction with the formation of nitrite ofohromium in the solution.

Although I have specified chromium as the leather-forming metal in' allof the foregoing examples and prefer to use it, Ido not confine myselfto the use of the salts of this metal; but my invention includes the useof the salts of the other leather-forming metalsiron and aluminium.Where the salts of iron and aluminium are used, the same proportions andformulas as those given above for the use of chromium will be efficient,of course observing the difference in molecular weight; nor do I confinemyself to the use of the specific nitrites of the alkali metals named,but include the use ofany soluble nitrites of an alkali metal or of analkaline earth and also the use of nitrogen trioxid (N 0 and oxids ofnitrogen, which are convertible by reduction or oxidation into nitrogentrioxid, (N O such as nitrogen tetraoxid, (N O in the one case, andnitrogen dioxid, (N 0 in the other case, in Whichever way they areapplied to the leather-forming metal or its salts for the formation of atanning-bath containing a nitrite of a leather-forming metal in aqueoussolution. Of course when desired in compound metal tanning the salts oftwo or more leather-forming metals may be used, so as to form thecorresponding nitrites in the tanning solution. In practice, forinstance, I take for every one pound of chrome-alum one-half pound ofnitrite of sodium and dissolve the salts in water in proportions offromone part of the mixed salts to eight parts of water,

according to the strength of the solution de-' tanning with chromicsulfate and barium nitrite I take for every one pound of chromicsulfate, Cr (SO +-IS(H O,) one pound of ba rium nitrite, Ba(NO anddissolve the salts in water in proportions of from one part of the mixedsalts to eight parts of water, up to one part of the mixed salts toeighty parts of water, according to the strength of the solutiondesired, and so on for the other salts of the different leather-formingmetals. I have found four ounces of chromium nitrite to each gallon ofwater to bean efficient tanning liquor.

Of course my invention contemplates and comprises all methods ofintroducing into the bath or generating within the bath a nitrite of aleather-forming metal. For instance, I

can introduce into a bath containing chrome hydrate in suspension astream of nitrogen trioxid (N 0 through a tube in quantities sufficientto dissolve the chrome hydrate. Nitrite of chromium will be formed inthe bath.

My invention contemplates several diiferent methods of using mytanning'solutions, thus, first, subjecting the skins or hides to theaction of an aqueous solution containing a nitrite of a leather-formingmetal and subsequently subjecting the skins or hides to the action of anorganic tanning liquor such as is made entirely from sumac, oak,hemlock, and other barks and materials containing tannin; second,subjecting the hides or skins to the action of an aqueous solutioncontaining a nitrite of a leather-forming metal, and subseqentlysubjecting the skins or hides to the action of a metallic tanning-bathin which the nitrite ofa leather-forming metal is not present; third,subjecting the skins or hides to the action of an organic tanning liquorinto which a nitrite of a leather-forming metal or nitrogen trioxid (N 0or an oxid of nitrogen which is convertible by reduction or oxidationinto nitrous oxid has been introduced; fourth, subjecting the skins orhides to the action of a metallic tanning liquor containing a nitrite ofa leather-forming metal or a metallic tanning liquor into which a saltof a leather-forming metal and either (a) a nitrite of an alkali metalor of an alkaline earth or (b) nitrogen trioxid (N 0 or (c) an oxid ofnitrogen which is convertible by reduction or oxidation into nitrogentrioxid (N 0 have been introduced; fifth, subjecting the skins or hideswhich have been previously tanned in an organic tanning liquor to theaction of a nitrite of a leather forming metal or the materials forforming such nitrite in aqueous solution, or, sixth,

subjecting the skins or hides to the action of an ordinary metallictanning liquor, and sub-.

sequently subjecting them to the action of a nitrite of aleather-forming metal or materials for forming such nitrite in aqueoussolutions.

The following are methods of practicing my invention: In cases whereskins have already been tanned either in organic or metallic tanningliquors I subsequently subject them to the action of one of myabove-doscribed liquors containing a nitrite of a leather-forming metal,and the resulting imfor in all cases such proportions of the tan-' ningmetal and nitrogen trioxid (N 0 should be used as to form the nitrite ofthe leatherforming metal used. In cases where the skin has not beentanned and where it is desired to tan it by the conjoint use of anordinary tanning liquor (organic or metallic) and my liquor containing ametallic nitrite I proceed in one of the following ways: (a) I preparean ordinary organic or an ordinary metallic tanning liquor by theordinary methods and introduce into it one of my tanning liquorscontaining a nitrite of a leather-forming metal. Effective proportionsto be used are one part of one of my liquors to ten parts of theordinary tanning liquor. (b) If the metallic tannage only is desired, Ican prepare an ordinary metallic tanning liquor in the usual way andintroduce nitrogen trioxid (N 0 into it mechanically.

In all cases and under all conditions the object of my invention is tosubject the skins or hides, tanned or untanned, to the action of anitrite of a leather forming metal, whether such nitrite be used in anyordinary tanning-bath (organic or metallic) or in a liquor which is usedsubseqent to the use of an ordinary tanning liquor, (organic ormetallic,) and my invention contemplates all methods of forming suchnitrites of the leather-forming metals and all proportions in which theymay be used in or with the tanning liquor.

If one of my tanning liquors is used in connection with an organictanning liquor and (a) is introduced into the organic tanning liquoritself, the organic tanning liquor may be weakened to one-tenth of itsusual strength, and the proportions for the actual tanning bath may thenbe, for instance, ten parts of the weakened tanning liquor to one partof my tanning liquor. The skins or pelts will be tanned in aboutone-tenth of the time required for tanning in the ordinary organictanning-bath by itself. liquors is used (b) subsequent to the use of theordinary tanning-baths, (either organic or metallic,) the ordinarytanning-baths should be of their usual strength, and the skins or hidesmay be immersed in one of my tanningbaths from one to twenty-four hours,according to the thickness, character, and quality of the skin. If oneof my tanning liquors is If one of my tanning used in connection withone of the methods of ordinary metallic tannage and is introduced (a)into theliquor of a single metallic tanning-bath process, theproportions may be, for instance, ten parts of the ordinary tanningliquor of the ordinary strength to ten parts of one of my tanningliquors.

For the purpose of the following claims it is immaterial and it is anequivalent use of my invention whether the nitrite of theleather-forming metal is contained in the ordinary tanning liquor(organic or metallic) itself or is used in a separate liquor in whichthe skins or hides are previously or subse-' quently immersed.

Having thus described my invention, what I claim is- 1. The process oftanning which consists in exposing the skin or hide to the action of anitrite of a tanning metal in solution, and the ingredients of anordinary tanning liquor in solution, substantially as described.

2. The process of tanning which consists in exposing the skin or hide tothe action of a nitrite of a tanning metal in solution, and theingredients of an ordinary metallic tan;

ning liquor in solution, substantially as described.

OTTO P. AMEND. Witnesses:

HARRY V. FOUNTAIN, JAMES M. STEWART.

